1. Field of the Invention
The present invention relates to an ink jet printer and more particularly to an ink jet printer wherein ink is supplied to an ink tank disposed on a movable carriage from a main tank provided outside the movable carriage.
2. Description of the Prior Art
According to a known ink jet printer, a main tank is provided outside a movable carriage and ink is supplied (replenished) from the main tank to an ink tank disposed on the movable carriage.
For example, in Japanese Published Examined Patent Application No. Sho 54-31898 (hereinafter referred to as the “prior art reference 1”) there is disclosed a construction wherein a liquid reservoir filled with a liquid absorber is provided within a print head, and a wick provided in a liquid filling device is inserted into the liquid reservoir from a fill opening and is brought into contact with the liquid absorber, whereby ink is supplied to the liquid reservoir from the liquid filling device under the action of capillarity.
In Japanese Published Examined Patent Application No. Sho 60-9903 (“prior art reference 2” hereinafter) there is disclosed a construction wherein the amount of ink remaining in an ink tank disposed on a carriage is detected and if it is below a predetermined amount, the carriage is moved to a print stand-by position and ink is replenished to the ink tank by being dropped from a base tank provided at an upper position.
In Japanese Published Examined Patent Application No. Sho 63-51868 (“prior art reference 3” hereinafter) there is disclosed a construction wherein a sub-tank and a main tank both mounted on a carriage are connected together through a feed pipe and, when the ink in the sub-tank decreases, ink is fed under pressure into the sub-tank by pressing the main tank, while air present within the sub-tank is discharged through a discharge pipe into a bag-like container.
In Japanese Published Examined Patent Application No. Hei 7-51356 (“prior art reference 4”) there is disclosed a construction wherein a first tank disposed on a carriage and a second tank disposed outside the carriage are connected together through two connecting pipes and ink is fed under pressure from the second tank to the first tank through one of the connecting pipes, while an overflow is recovered into the second tank through the other.
Further, in Japanese Patent No. 2772014 (“prior art reference 5” hereinafter) there is disclosed a construction wherein, when a residual amount detecting electrode in a first ink tank disposed on a carriage detects reduction of the residual amount of ink, a mechanical valve in a tube which connects the first ink tank and a second ink tank disposed outside the carriage with each other is opened, whereby ink is replenished automatically from the second ink tank which is located at a higher position than the first ink tank.
The above conventional ink jet printers involve the following inconveniences.
In the prior art reference 1, a satisfactory ink shift cannot be done in some particular liquid distribution condition in the interior of the liquid reservoir, and the evaporation and denaturation of ink are apt to occur because the wick is exposed at all times.
In the prior art reference 2, the dropped ink adheres to a wall surface or the like and is denatured or solidified, which may obstruct printing.
In the prior art reference 3, the internal pressure of the sub-tank becomes a positive pressure because ink is fed to the sub-tank under pressure, and the positive pressure also acts on a print head orifice, causing the leakage of ink such as face-flood.
In the prior art reference 4, it is necessary that the first tank be disposed lower than a print head, and ink which has been increased in viscosity is pressurized so as to be discharged from the print head, so that ink is apt to leak from a connection.
In the prior art reference 5, there occurs ink leakage upon deterioration of the mechanical valve.